you need the large fuse, as there can often be a turn on surge with this pre it is worth going up a size and using the 6.3A. That’s what I used in my Ref 40. The black is good but the Blue is better and benefits from less need for burn in

Before Geoffy The Fuse Troll jumps in, remember that SR fuses are not UL or CSA approved. You still need a legitimate fuse to meet electrical safety bureau driven requirements. Otherwise, if there’s an electrical fire due to the equipment with the boutique fuse, your insurance claim will be denied.

Better be safe than sorry. Spend the extra several hundred dollars on music.

Just so I understand, these SR fuses work as protective fuses, correct? A SR 4 amp fuse should blow when that current is exceeded correct? I mean otherwise it's not a designed fuse and it's just a piece of metal. I'm not so concerned about the UL listing, I just want to make sure they blow when they are supposed to and that there is a performance spec associated with their design. I ordered a SR blue last week and now you guys have me worried about even using it.

What are you talking about? Ramtubes is talking about aftermarket fuses wrecking equipment because they don't do their primary job.

Look .. if you want to buy the snake oil and risk fruit your gear, have at it. But why spend $50 to do what a 2 cent piece of 16g wire will do? If you're not worried about killing your gear, just bridge the fuse holder with a piece of wire or bus bar. If you are worried about frying your gear, use a fuse proven to do it's job. This kind of analysis takes no brains. If you are chasing aftermarket fuses as solutions, you're just gullible.

There was a thread a few years ago regarding aftermarket fuses and the possible dangers of using them. The subject was not about whether or not there is an audible difference vs. stock. Many of our resident experts participated and the result was there were no reports of components being fried or catching fire if the proper value fuse was used.

Regardless of which fuse blows when and what manufacturer it was, how many of you have actually had any of the fuses blow? I have never had it happen, may be just a pure luck, or have never heard it happen to anyone I know.

@glupson I recently had an AC fuse in my IEC connector blow when switching from triode to UL mode. Turn on and switching surges popping fuses is not as uncommon as you may think. In fact you can search the forum and find others here posting about it over the years.

" I have had plenty of fuses blow because my amp has a massive power supply ". Many amps being sold have massive power supplies, and if fuses were to continue to blow, I think these amps would be right back to the manufacturer for constant repair, or replacement. Enjoy ! MrD.

Hey... If you don't believe me about tuning fuses frying stuff, listen to a guy who's seen it.

If you’re foolish enough to waste good money on boutique fuses, add an additional real fuse in line with the boutique fuses so there’s some real protection. Boutique fuses aren’t UL or CSA approved or tested in any meaningful way.

If you’re foolish enough to waste good money on boutique fuses, add an additional real fuse in line with the boutique fuses so there’s some real protection. Boutique fuses aren’t UL or CSA approved or tested in any meaningful way.

PADIS fuses are UL, PSE and SEMKO approved and they are "boutique" fuses.

three_easy_payments, kosst_amojan, analogluvr, mrdecibel, and anyone who I might have missed,

Thanks for responses. I believed fuses may blow, they would not be putting them in otherwise, but was wondering how common that really is. I guess more common than I observed. Maybe mrdecibel and I are simply lucky.

In my case the blown fuse was a little bit of user error as well as a little manufacturer error. I was listening pretty loud when I switched on the fly from the triode to UL, instantly doubling the watts. Later in discussing with the manufacturer, they recommended using a 4 amp fuse instead of the 3 amp fuse that came with the amp stating that you can usually get away with a 3 amp fuse but switching surges can sometimes pop the 3 amp. Since then I always reduce the volume when switching from triode to UL and have never had a problem since, even with a 3 amp fuse.

I understand you’re a bit weak on electronics theory, but I’ll try to explain.

Like I said above, my amp uses very simple in-rush current limiting. In-rush current is the amount of power the amp draws when you turn it on. My amp uses nothing more than a pair of NTC CL60 thermistors to limit the in-rush. Once they’re warm they do nothing. You want to limit that because it can be a lot more power than the amp operates at. The in-rush is also very hard on rectifiers and the reservoir caps. My amp is a class A amp so it’s drawing all the power it will ever use just sitting there idling. It makes a lot of sense to fuse it as conservatively as possible to avoid damaging something more pricey that a 20 cent fuse. So... It’s not that it’s broken or poorly designed. It’s artfully simple in it’s design, as all Pass amps are. You want a fuse to be as close to popping as possible under normal use. The fact mine pop so easily indicates they’re well suited to doing their job.

So all that talk about other's poorly designed power supplies in their lousy amps and their boutique fuses was just a lot of hot air because you decided to build an amp that would often fail by design because you seem to think it sounds better that way?

You keep citing Nelson Pass's designs as the inspiration for yours and yet I've yet to hear of any fuses popping with regularity with his amps. If they did, we'd all hear about it by now and no one would be buying them.

You're obviously not at all familiar with the First Watt products. You know... Like the J2 that got Stereophile's Amp of the Year award. Mine is a modified clone of the F5. The power supply in it is actually more muscular than what Nelson built the First Watt F5 with. The fuse pops at 300 watts like in all FW amps, but because mine runs 32V rails instead of 24V at the same 120,000uF reservoir capacitance, the in-rush current is a bit higher. All the First Watt amps will pop their fuses if you shut them off long enough to disconnect inputs then power them back on. It's just long enough to drain the PS caps, but not long enough to let the thermistors cool.

I don't blame you for being clueless about FW amps. They're really nice amps for people looking for something different than you're typical idiot-proof production line amp. They're all hand built and adjusted by one guy; either Nelson Pass or the DIY'er who built it. Simplicity wins the day. No need for idiot-proofing here.

The only fuses I've used in recent years that blew were SR Black fuses I was testing for their sound. Also, I concluded that they had no impact on the sound of the components I stuck 'em in, and after testing I sent the pile of them back to my source. I'm sticking to Littelfuse and other stock fuses that work fine and, like any other well sorted fuse, have zero impact on the sound except when they melt.

Sorry if you've spent your life listening to mass production amps with torpid little power supplies. My amp is 31 watts per channel with a power supply rated for 400 watts per rail. Not sure what you're listening to, but I've never heard of a class AB amp that over-built. That's a 31 watt amp that won't show a clipped waveform until you reach up around 120 watts into 8 ohm. And there are guys that drop 2 of those into their amps. You'd be a complete fool not to fuse something like that conservatively.

I’ve been in the fancy fuse game ever since Isoclean, yes they’re UL rated, came on the scene nearly 20 years ago. So, I was one of the first. But I never had a fuse blow. I’ve also had Audio Magic Nano fuse. Never blew. Boy, was I lucky!

kosst, I will say this. You are relentless, and have an amazing amount of energy that spurs from your mouth ( fingers ). Why can't you let it go, and leave this fuse thing to us listeners who hear it and benefit from it. It is our money, it is our journey, and has nothing at all to do with you. And let it be said, we, as a group, have nothing we need to prove to you. Who are you anyway, the fuse police ? And keep in mind, I am not discussing fuse direction here, just the change of the fuse. Enjoy ! MrD.

@nonoiseSorry pally, but none of those amps have power supplies as over-built to the demands of the amp as mine. Marantz has certainly never made anything that comes close. As Nelson put it, it'll drive a 2 ohm load without burping. And when you look at the numbers it's obvious why.

@mrdecibelIf this is your platform to sell people on fuses, then it's my platform to dissuade people from silly fuses. I just want it to be clear to the crowd that somebody with a little technical knowledge thinks this is nonsense. And I'm not the only one who gears nothing out of these goofy fuses. If having your ideas and statements scrutinized is unpleasant, perhaps exposing your ideas and statements to the world isn't the right choice. I enjoy contending with people. It makes me go out and learn things and I learn from them. But so far I haven't learned anything from the fuse folks. There's just nothing to learn.

If this is your platform to sell people on fuses, then it's my platform to dissuade people from silly fuses.

The problem with this declaration is that I don't see anyone here trying to "sell people on fuses." Rather, there are some posters who share their experiences about fuses. You seem to want to disrupt that conversation.